Sahih Muslim Book 8, Hadith Number 3353.

Chapter: When one is invited to a wedding feast, one should accept it.

Abu Haraira (Allah be pleased with him) reported Allah’s Apostle (May peace be upon him) as saying. The worst kind of food is at the wedding feast from which one who comes is turned away, and he who refuses it is invited, and he who did not accept the invitation disobeyed Allah and His Messenger (May peace be upon him).